Heating cooking pots inductively has the advantage that the heat is produced directly in the cooking pot and thus there are no problems of transmitting the heat. In order to control the power, either the operating frequency can be altered or the output can be clocked. Difficulties do admittedly arise as a result of the slight inertia of the inductive cooking point, because the timing pulses would have to follow each other rapidly. However, the suggestion has been made in German Offenlegungsschrift No. 2633741 of clocking the high frequency which is conveyed to the induction heating coil at such a rapid clock rate that a smoothing capacitor can be used to receive fluctuations of current at its input and reduce or eliminate feedback to the mains of what would otherwise be a fast timing pulse sequence.
In the known cooking apparatus which are heated inductively, adjusting the power is carried out manually by means of a power control. Using a temperature-dependent control presents difficulties. The cooking surface, that is, the supporting surface for the cooking pot, consists preferably of non-metallic material. If metallic material is used, then this could only be non-ferromagnetic material, which does not present a magnetic screening to the induction coil and which receives substantially no power as a result of the relatively deep penetration of the electromagnetic flux lines therein. In order to achieve the full advantages of an induction cooker, this relatively thin supporting surface for the cooking pot must extend over several cooking points. For this reason, openings for temperature sensors would be undesirable because the stability of the supporting surface would suffer greatly because of this. Also, the openings would prevent the chamber located below the supporting surface from being protected against the intrusion of damp and other undesired substances.
Other contact heat sensors would also be unsuitable since their use would impose a requirement for the use of a cooking pot having an absolutely flat base, which is otherwise not necessary for inductive heating. In any case, the reproducibility of the temperature control would be poor.